I was going to reply it was some kind of redundancy, the word is not needed there.
I guess we didn't understand the question the same way.
Indeed; @Car: just so you are aware, the construction "Antes de deixar o hotel, ..." would also work (you can think of this as a translation of "Before leaving the hotel,..."), and that just uses a regular infinitive (which I presume from your question, and your two stars in Spanish, doesn't confuse you). The construction with the personal infinitive is more like "Before you leave the hotel,...". There's is little to no difference in meaning between the two, AFAIK.
The article I linked to mentions that the personal infinitive stands in for the present subjunctive in constructions like these, which would imply that it's possible to say "Antes que você deixe o hotel, ..." - I can't confirm if that's correct, I would never say it that way (I would use the personal infinitive construction here almost always I think), @Osias, does "Antes que você deixe o hotel, ..." sound like something a native speaker would say?